1. Field
Embodiments relate to a light scanning unit (light scanner) and an electro-photographic image forming apparatus employing the same, and more particularly, to a light scanning unit (light scanner) capable of reducing directivity of profiles of dots of an exposed beam, and an electro-photographic image forming apparatus employing the same.
2. Description of the Related Art
Electro-photographic image forming apparatuses such as a laser printer, a digital copier, and a multi-function printer have a configuration in which a laser scanning unit scans light onto a photoconductor that is uniformly electrified by an electrifier so as to achieve selective exposure and thus to form an electrostatic latent image, the formed electrostatic latent image is developed as an image by using a developing agent such as a toner, and the developed image is transferred to a print medium.
In an image forming apparatus, in order to obtain a color image, a plurality of developers accommodating a plurality of different color developing agents (toners) are disposed around a photoconductor such as a photosensitive drum, a developer accommodating a predetermined color toner is disposed to face the photoconductor so as to develop an electrostatic latent image, an image of the toner is transferred to a recording medium, and the above developing and transferring operations are performed for the other colors.
In a conventional image forming apparatus, in consideration of an inner size of the conventional image forming apparatus, positions of components such as developers disposed around a photoconductor, and prevention of a ghost effect due to secondary reflective light of a beam reflected on a surface of the photoconductor, a sufficient incident angle is set to a beam incident onto the photoconductor.
Also, in a color image forming apparatus, when a color image is formed by overlapping single-color images on a recording medium, since locations where the images are recorded are inevitably slightly offset from each other, a stain or a moire pattern is generated due to inappropriately mixed colors. In order to prevent this problem, a conventional color image forming apparatus sets different screen angles to different color images. As such, even when locations of the color images are offset, colors may be constantly maintained and a moire pattern may be prevented. A combination of screen angles that are broadly and generally used in print apparatuses is a combination of yellow 0°, cyan or magenta 75°, black 45°, and magenta or cyan 105°.
Currently, in order to reduce a total size of a color image forming apparatus, a distance from a laser scanning unit to a photosensitive drum is decreased. As such, a main scanning direction incident angle of a beam on the photosensitive drum is increased and thus a profile of an exposed beam is distorted. Also, in order to achieve a high-quality color image, a high resolution mode (a large number of lines per inch (LPI)) is applied. In order to achieve a large LPI, since a distance between dots on a surface of a photosensitive drum is reduced and interference occurs between a profile of an exposed beam and a screen angle, the uniformity in color densities on paper may be reduced, colors may be offset, and thus image quality may be reduced.